This paper compares the measurement results obtained from three different implementations of measuring receivers regarding spectral level accuracy. The objective is to validate the suitability of direct sampling electromagnetic emissions measurements with respect to those delivered by a high-end EMI receiver in frequency swept and FFT modes. The experimental setups follow the verification methods described in the ECSS-E-ST-20-07C Rev.2 standard to set realistic and reproducible conditions. Between 50 kHz and 100 MHz, common mode and differential mode currents are measured when multisine excitation signals with controlled amplitude profiles are used as references. Subsequently, conducted and radiated emissions tests are run to investigate the correlation between measurements with the different receivers. The instruments used are a low-cost USB digitiser Picoscope PS5444D, a high-performance benchtop oscilloscope R&S RTO6 and the R&S ESW44 full-compliant EMI test receiver. The analysis concludes that the emissions measurements performed with the direct sampling approach are excellent for the intended application, exhibiting an accuracy comparable to the dedicated EMI test receiver and a well adequate dynamic range and noise level.

The project (21NRM06 EMC-STD) has received funding from the European Partnership on Metrology, co-financed by the European Union's Horizon Europe Research and Innovation Programme and by the Participating States. EMC Barcelona's project under grant number SNEO-20211223 has received funding from CDTI, which is supported by "Ministerio de Ciencia e Innovación" and financed by the European Union - NextGenerationEU - through the guidelines included in the `Plan de Recuperación, Transformación y Resiliencia". Dr. Azpúrua has received funding from the StandICT.eu 2023 project, financed by the European Union's Horizon Europe - Research and Innovation Programme - under grant agreement No. 951972. Dr. Pous' work was supported in part by the European Union's Horizon 2020 research and innovation programme under Marie Skłodowska-Curie grant agreement No. 801342 (TecniospringINDUSTRY) and the Government of Catalonia's Agency for Business Competitiveness (ACCIÓ) and in part by the Spanish "Ministerio de Ciencia e Innovaci´on" under project PID2019-106120RBC31/AEI/10.13039/501100011033.